Our overall goal is to investigate the immunobiology of tumors with respect to the nature of tumor antigens and the immune responses that these antigens evoke. This proposal is for continuation of work now funded by an investigator initiated contract. We are studying the cell surface antigens (CSA) of primary and transplanted methylcholanthrene (MCA)-induced mouse sarcomas, using serological techniques, including the individually unique tumor-specific transplantation antigen (TSTA), antigens related to expression of endogeneous murine leukemia virus (MuLV), differentiation and tissue specific antigens shared by tumor cells and certain normal cells. This work should also allow us to detect sarcoma specific antigens (if they exist). We have formulated five related specific aims: (1) to investigate MuLV associated CSA, (2) to study the antibody response of mice to syngeneic sarcomas, (3) to serologically characterize sarcoma CSA, using alloantisera and also the Milstein hybridoma techniquee, (4) to investigate transplantation immunity to unique and shared TSTA, and (5) to structurally analyze several of the serologically characterized CSA. Attempts will be made to correlate serological data with data on transplantation immunity. This work will be one of the first systematic studies of the CSA expressed on MCA-induced mouse sarcomas. It should help toward understanding their roles in tumor rejection and may also serve as a basis for a serological approach to other types of tumors, including such in man.